the managements ludicrous decision recently to make all simulator stand in duties assessable.
Stand in always was and will be double jeopardy. As a stand in during an LPC or OPC you are not required to do much except operate competently as PM for the vast majority of the time, if you can't cope with that then maybe you should be taking a look at your professional attitude.
If, as I suspect, you are referring to LOE's then these are just like doing a Line Check when it is your FO or Captain who is on check, effectively you are on check too, again all that is required is a competent level of performance, just like it should be on any day of the week.
As for the number of Stand Ins that you are rostered, have you spoken to Crew Planning, your Base Captain, or the relevant Manager to try to resolve the "issue"?